Lubricants are conventionally employed in the processing of rigid plastic materials such as polyvinylchloride, acrylonitrile-butadiene-styrene and polypropylene polymers to improve the process-ability of the polymer. These provide for internal dynamic lubrication for the polymer molecules by reducing the interactive force between polymer chains.
The addition of lubricants to rigid plastic materials generally does not enhance the early color and heat stability of the material. Glyceryl monostearates (GMS) have been used as lubricants in polyvinylchloride and have been observed to produce some enhanced heat stability. We have found, however, that if the glycerine content of GMS is appropriately limited, an unexpected degree of heat stability and enhanced early color results in the use of GMS as a lubricant.
Accordingly, it is the primary object of the present invention to provide an improved method for lubricating rigid plastic materials with enhanced heat stability using a GMS lubricant.
It is a further object of the present invention to provide enhanced early color in rigid plastic materials using a GMS lubricant.
Still yet a further object of the present invention is to provide rigid plastic materials having enhanced early color and improved heat stability.
These and other objects of the present invention will become more apparent from the following discussion.